1. Field of the Invention
The present invention relates to a pneumatic valve. More particularly, the present invention relates to a pressure-controlled valve for creating mechanical movement.
2. Description of the Related Art
A conventional air valve is typically installed between a vacuum pump generating a vacuum pressure and a reactor using the vacuum pressure. The air valve serves to connect the vacuum pump and the reactor when needed. Such an air valve is operated by air pressure and includes a bellows that can be constricted by an applied air pressure. One such conventional air valve includes a cylinder, a piston interior to the cylinder, and a valve shaft. A plurality of ports are included in the cylinder to allow pressurized air to be supplied to, or discharged from, a head of the piston. In response to such an inflow or outflow of air, the piston is forced in a reciprocating, straight-line mechanical movement. The straight-line movement of the piston is transferred to the bellows by the connecting valve shaft, which connects a central portion of the piston to the bellows using a nut. The movement of the bellows in turn opens or closes a ventilation passage of a valve body.
A significant disadvantage of such a valve configuration is that, over time, the nut may loosen due to the repeated movement of the piston, eventually causing the piston to be separated from the bellows. In order to re-attach the piston and the bellows or to tighten the nut the cylinder must be disassembled.
A feature of an embodiment of the present invention provides a pneumatic valve having an improved coupling mechanism between a valve shaft and a piston.
Another feature of the present invention provides a pneumatic valve having a piston with a long life span.
According to a preferred embodiment of the present invention, a pneumatic valve includes a cylinder having at least one gas port for providing an inflow and an outflow of a gas; a piston arranged in the cylinder that performs a reciprocating, straight-line movement in response to the inflow and outflow of the gas; a first valve shaft passing through the piston having a first end portion including a first coupling portion; and a second valve shaft including a second coupling portion and having a first end portion protruded from the cylinder, wherein the second coupling portion is coupled to the first coupling portion, such that straight-line movements of the piston are transferred in a longitudinal direction of the first and second valve shafts.
Preferably, the first and second coupling portions have a threaded interface capable of mating, wherein the first coupling portion includes a male threaded screw portion, and the second coupling portion includes a female threaded screw portion.
The second valve shaft further includes a second end portion having a flange portion contacting the piston. The first end portion of the second valve shalt includes a tightening protrusion that may be tightened using a tightening tool. The tightening protrusion may have a groove or a polygon-shaped protrusion. Preferably, the pneumatic valve further includes a bellows arranged around a second end portion of the first valve shalt, an elastic member arranged between an outer surface of the cylinder and the bellows, and a lubricant injection apparatus for injecting a lubricant, such as oil, to an inner surface of the cylinder through the second valve shaft, which preferably includes at least one lubricant passage therein.
The present invention provides several advantages over conventional air valves. One, since a connection between the first and second valve shafts may be tightened by tightening the protruding second end portion of the second valve shaft without disassembling the cylinder, a loosened coupling between the first valve shaft and second valve shaft may be facilely repaired. Second, since friction between the piston and an inner surface of the cylinder is reduced by the application of a lubricant, a pneumatic valve having a piston with a long life span may be achieved.
These and other features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon review of the detailed description that follows.